Modal Verbs Must, Have to, To be to

The modal verb MUST is used to:

1)To express the conclusion that something is certain, and to talk about necessity and obligation

E.g. You must be Anna's sister-you look just like her.

2)To express the conclusion that something is certain or highly probable - to suggest that there are excellent arguments for believing something.

E.g. There's the doorbell. It must be Roger.

3)must + perfect infinitive (have + past participle) to express conclusions about the past.

E.g. 'We went to Rome last month.' 'That must have been nice.'

4)To say what is necessary, and to give strong advice and orders to ourselves or other people.

E.g. Plants must get enough light and water if they are to grow properly.

British industry must improve its productivity.

5)“Must not” to say that things should not be done, or tell people not to do things

E.g. The government really mustn't  expect people to work hard for no money.

Note! must not/ mustn't is not used to say that things are unnecessary

6)To talk about obligation

E.g. You really must go to church next Sunday-you haven't been for ages.

7)To give orders or instructions for the future. E.g. You can borrow my car, but you must bring it back before ten.

 The modal verb HAVE TO is used to: 

1)To talk about an obligation that comes from 'outside' (for instance a regulation, or an order from somebody else)

E.g. I have to work from nine to five.

2)To express the conclusion that something is certain

E.g. This has (got) to be the worst job.

3)To talk about necessity

E.g. This is a lovely party, but we've got to go home because of the baby-sitter.

4)To talk about obligation

E.g. Catholics have to go to church on Sundays.

5)Will have to can be used to 'distance' the instructions, making them sound less like direct orders from the speaker. E.g. You can borrow my car, but you'll have to bring it back before ten.

6)“Had to” is used to talk about past obligation.

E.g. Edna isn't in her office. She had to go home. (= It was necessary for her to go home.)

 The modal verb TO BE TO is used to: 

1)Prearranged necessity, part of a plan in the present or future

E.g. When is the wedding to be?

E.g. I was to meet my mother at 11.

2)The plan which wasn’t carried out

E.g. He was to have come at 6 but it is 7 and he hasn’t come.

3)Strict order

E.g. You are to stay here till father comes.

4)Strict prohibition

E.g. You are not to do it!

Elementary Exercises 

Exercise 1

Exercise 2

Exercise 3

Exercise 4

Exercise 5

Exercise 6

Exercise 7

Exercise 8

Exercise 9

Exercise 10

 Intermediate Exercises
Exercise 1
Exercise 2
Exercise 3
Exercise 4
Exercise 5
Exercise 6
Exercise 7
Exercise 8
Exercise 9
Exercise 10

Advanced Exercises
Exercise 1
Exercise 2
Exercise 3
Exercise 4
Exercise 5
Exercise 6